While applicable to other musical instruments, this invention will be described with particular reference to touch-actuated stringed musical instruments, of which the so-called touch guitar is an example, in which the vibration of the string which produces the musical sound is initiated by depressing the string against an underlying substrate, typically the fingerboard or a fret, the resulting vibration of the string being used as a source of the desired musical sounds without requiring any plucking, bowing or strumming of the strings. Aside from the fact that such action makes possible appreciably different musical sounds unique to such touch operation, it also makes possible the use of both hands in fingering the strings, since neither hand is needed for plucking, bowing or strumming, for example. This has made possible a dual-neck guitar, for example, having six strings on one neck for playing with one hand and four other strings, typically the bass strings, mounted on another neck for playing with the other hand. One difficulty with such instruments is that when the string is released at the intended end of a note, it is left free to vibrate at its natural open string frequency, and this not only provides a continuance of sound beyond when it is desired that it terminate, but also produces a frequency or tone which is other than that desired. For this reason, it has been found highly desirable to eliminate sound produced by the vibrating string very shortly after it is released, i.e. to mute the system at such times.
This has been accomplished, at least to some degree, by placing against each string a damping substance such as a body of felt, whereby when the finger is removed from the string the vibrations will be rather rapidly damped out by the felt. This, however, has been found to be somewhat unreliable with respect to the extent of damping provided under different conditions, and of course is also not adjustable; in addition, if applied so as to heavily damp the string after it is released, it will also tend to damp the string during the desired activation intervals.
Another known arrangement for muting or damping the string vibrations utilizes an electrical muting circuit. An electrical pickup senses the vibration of the strings and produces a corresponding electrical signal which is amplified in electronic circuitry to provide the final audible output of musical sound; within this electronic circuitry there is located a mute circuit, which prevents the electrical signals from passing to and through the amplifier until a string produces an audio signal large enough to operate a control circuit for the mute device which renders the mute ineffective, so that the audio tone can then pass to the final amplifying stages; when the string is released, the vibrations of the strings die down to a point where the corresponding electrical signal level falls below a certain threshold, and the muting circuit then mutes the audible effects of any continuing vibration of the string.
This arrangement has also been found to have a number of drawbacks. First, in order for the mute circuit to be deactivated and an output produced, the string vibrations must increase to a certain level, and it is not until this occurs that the output sound occurs; this means that at least a small amount of the initial sound, or attack, may be missed or distorted slightly when the string vibration first occurs. Secondly, the point at which the mute circuit is turned on and off depends upon the strength or loudness of the string vibration; for loud sounds the mute will be turned off faster, but will also remain off longer, than for soft sounds produced by small string vibrations. The latter type of system typically includes a controllable amplifier stage designed so that for very soft playing the gain can be increased to remove the muting more promptly and to reinitiate muting more gradually, thereby to provide a more natural sounding termination. For large vibrations of the strings, this amplifier would normally be turned by the operator to a lower gain setting. However, to adjust the gain for various levels of input is obviously difficult, especially where loud and soft passages follow each other in the same musical piece. In addition, when the gain is turned up to a high level to accommodate small string vibrations, the system tends to become "hot", in that very small vibrations of the instrument itself due to handling, or even feedback from the output amplifiers may induce a string (particularly an open string) to vibrate sufficiently that it can deactuate the mute circuit and produce undesired output sound.
Accordingly, it is an object of the present invention to provide a new and improved system for the muting of stringed instruments.
Another object is to provide such muting system which is affirmative and predictable in operation, and readily controlled and arranged to provide predetermined optimum effects.